Input devices are used in many technical systems, such as, for example, in screens, mobile telephones, motor vehicles and tablet computers, etc.
Touch-sensitive surfaces are increasingly being used in input devices. Such surfaces are to be operated intuitively and, in combination with a display unit, can give a user optical feedback when touched. An input device can further comprise a force sensor which detects the application of a force to the touch-sensitive surface. For example, a user can move a mouse pointer onto a switch symbol by means of the touch-sensitive surface and trigger operation of the switch symbol by applying an increased force to the touch-sensitive surface.
Input devices of the above-mentioned type are also used inter alia in mobile or machine-oriented areas in which they are exposed to vibrations. Such areas include, for example, mobile telephones, sports electronics, vehicles or industrial machines. Any vibrations which occur here can lead to unintentional operation of the input device. The reason for this is, for example, acceleration of the input device or of a user due to acceleration, so that the user unintentionally touches the touch-sensitive surface or exerts increased force thereon. The input device can misinterpret this as inputs.
Erroneous inputs can lead to loss of time, miscommunication and accidents. When operating motor vehicles and other machines in particular, corresponding safety considerations play a major role.
Publication US 2009/0243817 A1 discloses an input device which is able to detect touches and force applications by means of a matrix of capacitive sensors. The input device is equipped with an acceleration sensor in order to disregard force applications when vibrations are detected by the acceleration sensor. However, because both the force application and the touch are detected by the same sensor system, the input device is not able to distinguish reliably between a user-generated vibration and an external vibration. An excessively forceful input by a user could be misinterpreted as external vibration and wrongly discarded.